Stellar classification is the categorization of stars based on their spectral characteristics. The modern Morgan–Keenan (MK) system uses the letters O, B, A, F, G, K, and M to sequence stars from the hottest (O type) to the coolest (M type).
The Solar Neighborhood contains stars within a few light-years of the Sun. These include Proxima Centauri, our closest stellar neighbor, and other systems that help us understand stellar evolution.
The Solar Neighborhood contains stars within a few light-years of the Sun. These include Proxima Centauri, our closest stellar neighbor, and other systems that help us understand stellar evolution.
Spectroscopy
Reading Chemical Composition
Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light and radio, which radiates from stars and other celestial objects. It reveals information about composition, temperature, and motion.
First Used: 1814 by Fraunhofer
Discovery: Helium on Sun first
Lines Cataloged: 25,000+ (solar)
Spectral Analysis: Spectroscopy involves dispersing light into its component colors to create a spectrum. By analyzing the specific wavelengths of light absorbed or emitted by celestial objects, astronomers can determine their chemical composition, temperature, and motion through space.
Doppler Effect
Detecting Stellar Motion
The Doppler effect is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. In astronomy, it is used to measure the speed at which stars and galaxies are approaching or receding from us (blueshift or redshift).
Discovered: 1842 by Doppler
Blueshift: Approaching star
Redshift: Receding star
Doppler Shift: Just as a car horn sounds higher-pitched when approaching and lower when receding, light waves behave the same way. When a star moves toward us, its light is compressed to shorter, higher-frequency wavelengths — a blueshift. When it moves away, the light is stretched to longer, lower-frequency wavelengths — a redshift. This principle allows astronomers to measure the radial velocity of distant stars and galaxies from Earth.
Stellar Classification
O B A F G K M
Stellar classification is the categorization of stars based on their spectral characteristics. The modern Morgan–Keenan (MK) system uses the letters O, B, A, F, G, K, and M to sequence stars from the hottest (O type) to the coolest (M type).
Our Sun: G2V yellow dwarf
Most Common: M-class red dwarfs
System: Morgan-Keenan (MK)
Stellar Types: Stars are classified by their spectral characteristics, primarily using the Morgan-Keenan (MK) system which arranges them from hottest to coolest: O, B, A, F, G, K, M. This classification reveals vital information about a star's temperature, composition, and evolutionary stage.